Thyroid Eye Disease: Why Do Eyes Bulge?

If you or someone you love has thyroid problems, you may have noticed a change in the eyes — they seem to push forward or look more open than usual. Sometimes the very first sign isn't bulging at all: it's dry, watery, red, irritated eyes that bring a patient into my chair, and only then do we discover the thyroid connection. This is Thyroid Eye Disease, or TED — and understanding why it happens makes it much less mysterious.

What's happening behind the eye?

Think of your eye socket (the orbit) like a fixed-size bony cup. Inside that cup sit:

1. Extraocular muscles — the tiny muscles that move your eye
2. Orbital fat — the cushion supporting the eye
3. The eyeball itself (the globe)

In TED, your immune system mistakenly attacks the tissues behind the eye. This is autoimmune inflammation — research points to an immune recognition problem, most often riding along with Graves' disease (autoimmune hyperthyroidism). It doesn't attack the eye itself; it inflames the muscles and fat around and behind it.

When those tissues inflame, two things happen: the eye muscles swell and thicken (interestingly, the tendons at the muscles' ends are usually spared — a clue I look for), and the orbital fat expands. Because the bony socket can't expand, all that extra volume has nowhere to go — so it pushes the eyeball forward. That's the bulging, the exophthalmos (or proptosis) you see.

Normal orbit vs. TED orbit: healthy — slim muscles, normal fat, the eye sits comfortably in its socket. TED — inflamed, swollen muscles and expanded fat shove the eye forward, and the lids can't quite do their job.

The 3 classic signs I look for

TED doesn't just cause bulging. It changes how the eyelids work:

1. Proptosis — forward bulging. The most obvious sign. The eyeball is physically pushed forward, which can make full lid closure difficult — and an eye that can't close dries out and risks corneal damage.
2. Lid retraction (Dalrymple's sign) — the stare. The upper lid gets pulled higher than normal, exposing more white above the iris. That wide-eyed, staring look.
3. Lid lag (von Graefe's sign) — lids that don't follow. When you look down, your upper lid should glide smoothly with your eye. In TED it lags behind. I test this by having you follow my finger downward.

Before any of that, though, many patients just notice dry, gritty, watery, or red eyes — sometimes with light sensitivity or a feeling of pressure behind the eyes. If you have thyroid disease and your eyes start acting up, don't dismiss it as allergies. Tell your eye doctor about the thyroid history; it changes what I look for.

The chain reaction, simply put

Autoimmune trigger → inflammation plus buildup of gel-like sugars (glycosaminoglycans) in the orbit → eye muscles enlarge, fat increases → eye pushed forward, eyelid changes appear. It's not the eye misbehaving — it's the immune system redecorating the neighborhood around it.

How TED is diagnosed

You can't diagnose it by looks alone. It takes three parts, usually with your thyroid doctor and eye doctor working together:

• Thyroid function tests — blood work checking hormone levels
• Antibody tests — especially TSI or TRAb antibodies seen in Graves' disease
• A full eye examination — measuring proptosis, checking eye movements, eyelid position, vision, and optic nerve health

One thing patients find surprising: you can develop TED even when your thyroid labs look normal — and it can show up before, during, or after the thyroid problem itself.

FAQ

Is TED the same as Graves' disease? Not exactly. TED is most common with Graves' hyperthyroidism, but they're separate conditions.

Will both eyes be affected? Often yes, though one may bulge more. In about 10% of people, only one eye is noticeably involved.

Is the bulging permanent? TED usually runs an active inflammatory phase (6 months to 2 years), then quiets down. Redness and swelling often improve — but some bulging, retraction, or stare can remain without treatment. Early treatment limits long-term change.

What makes it worse? Smoking — the single biggest modifiable risk factor, by a wide margin. Uncontrolled thyroid levels don't help either.

What helps day to day? Artificial tears for dryness, sunglasses for light sensitivity, sleeping with your head slightly elevated to ease morning swelling, and taping lids shut at night if they don't close fully. Check with your doctor first.

When is it urgent? Sudden vision loss, double vision that won't quit, intense eye pain, marked redness and swelling, or bulging so severe the eye won't close — the optic nerve or cornea may be at risk. Don't wait.

How is it treated? Depends on severity: managing thyroid levels, selenium in mild cases (only on your doctor's advice), anti-inflammatory medications, and for severe cases, specialized infusion therapies or orbital surgery to create more room. An oculoplastic specialist guides the advanced end.

Educational information only — this doesn't replace medical advice. Talk to your healthcare provider about any eye or thyroid symptoms.

If your eyes have started telling a story your thyroid might have started — dryness, staring, bulging, double vision — come let me read it. Catching TED early is everything.

I'm Paddy Kalish, OD — an optometric physician in Brookline, MA. Thyroid patients: add a comprehensive eye exam to your care team at 1296 Beacon St — book online at paddykalish.com or call/text 857-314-4645.

Author

Paddy Kalish OD, JD and B.Arch Author and Blogger